Atomaria lewisi Reitter, 1877
First recorded from Britain and, it would seem, from Europe, from single specimens found among a heap of grass cuttings in a domestic garden in South-East London during May and October 1937 (Allen, 1938). The species now occurs generally throughout England and Wales north to the midlands, beyond this there are scattered records to the very North of Scotland. Island records extend from Scilly to the Shetlands (NBN Nov. 2011).

It is common throughout our Watford area and often occurs in large numbers; we have found them by sweeping low vegetation on a variety of habitats but in warm weather they seem to be most abundant from open and dry grassland e.g. from Cassiobury park or Common moor. They are often common among extractions from leaf litter and decaying vegetation from most habitats and they come readily to light; we have recorded them in abundance at m.v. in domestic gardens and along arable borders at Whippendel Woods. Allen (1998) considered this to be the most abundant species of the genus at m.v. We have recorded them each month from March to November and it is likely they occur throughout the year; Whitehead (1990) records adults in early January.

This very distinctive species soon becomes familiar; it varies subtly in shape and colour and there is a marked sexual dimorphism which, for a while, lead us to believe we were dealing with two species but, despite this, with a little experience they become obvious. Quoting Allen (1938) ‘Even in the field it could hardly be confused with any other species, except perhaps Zetterstedti, which, however, has a quite different habitat. (A. Zetterstedti is a very local South-Eastern species occurring in marshes and on Salix catkins, here the pubescence is very fine and decumbent and antennal segments nine and ten are much less transverse.) Relatively large for the genus; 1.4-2.0mm (FHL vol.13). Entirely testaceous, including appendages, although this varies from pale yellow to rather dark and often the pronotum is a little darker than the elytra, a feature we see mostly in the males.
Head shiny, finely and moderately densely punctured, pubescence sparse and coarse. Width across eyes slightly less the between front angles of pronotum. Eyes protruding and coarsely faceted. Clypeus produced to a point between antennal insertions. Distance between antennal insertions less than length of first antennal segment. Basal antennal segment curved and expanded apically; apex 1.5 to 2 times width at base, and long; 1.5-2 times longer than width at apex. Second segment much narrower and shorter; about 2/3 as long as basal segment. Third segment as long as second but narrower. Segments 4-8 subequal, club broad and distinct; segment nine and ten strongly transverse-some manipulation is generally needed to appreciate this. Terminal segment about as broad as penultimate.
Pronotum convex and shiny, punctures deeper and more distinct than those on head and elytra; distance between punctures about half a puncture diameter. Very finely bordered laterally and basally. Widest about middle, the lateral angle varies a little so that the narrowing towards the base is not always so strong. With a generally distinct (varies) and somewhat flattened transverse depression in front of basal margin, in some specimens this reaches the lateral margin.
Elytra broadest about middle and evenly curved to base and apex, the male is a little narrower and this soon becomes obvious. Pubescence long and overlapping, erect and curved so that the vestiture lies well above the elytral surface, this is obvious from above where it stands out from the elytral outline. Towards the base and, especially, around the humeral prominences there are usually a few fully erect setae giving the pubescence a bristling appearance. Suture finely bordered, this border diverges slightly about a fifth of the elytral length from the apex so giving the impression of a narrow subapical opening. Puncturation shallow and sparser than on pronotum; separation at least a puncture’s diameter. Surface varies; most often smooth and shiny but sometimes finely wrinkled so that punctures are indistinct and the elytra appears a little less shiny than the pronotum.

References

Allen, A.A. 1938 Ent. Mon. Mag. 74: 82-83
Allen, A.A. 1998 Ent. Rec. J. Var. 110: 153
Whitehead, P. F. 1990 Ent. Rec. J. Var. 102: 170

Female

Male

Aedeagus

Spermatheca

Antenna

Apex
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